Project Summary Hydrogen Sulfide is a gasotransmitter of biological and clinical relevance. In mammalian physiology, H2S is involved in regulation of certain cellular processes, playing significant roles in neuronal, cardiovascular and endocrine systems. While present during healthy cellular function, its presence and concentration are thought to be indicative of certain pathological states. For example, it is suspected to play important roles in conditions associated with human health including diabetes, hypertension, atherosclerosis, heart failure, inflammation, neurodegeneration, sepsis, and asthma. However, precise information is missing regarding the actual amounts of hydrogen sulfide that may be indicative of disease states. Estimates of healthy/normal levels in certain tissues vary widely, which is in part due to the lack of both sensitive and rapid methods to quantify the levels of H2S in vivo. Developing such a method/tool is critical to improving our knowledge regarding the biology of H2S and to eventual recognition of its clinical importance. An important and mainly overlooked consideration of H2S measurement is that, at physiological pH, most H2S is actually present as its conjugate base, HS?. Few, if any, measurement techniques seek to exploit this equilibrium. In other words, few have looked at detecting the hydrosulfide anion directly as a total sulfide measurement. We propose to exploit this surprisingly underdeveloped pathway for H2S quantification. Aligned with this approach, the Johnson/Pluth/Haley labs have demonstrated the first class of receptor molecules that bind HS? reversibly with high specificity and selectivity through exclusively non-covalent, reversible interactions. These arylethynyl receptors enable for the first time the development of ChemFETs with specificity and sensitivity for HS?. The assembled team of researchers, led by Dr. Fontenot, has recently demonstrated a similar development pathway by creating nitrate-selective ChemFET sensor that utilizes a similar arylethynyl receptor specific for nitrate. Given this past success with a similar analyte and technology, we hypothesize that the HS? receptor from Pluth/Johnson/Haley labs can be used to produce a HS? ChemFET. If successful, this will provide biomedical researchers with the opportunity to measure HS? in real-time and with minimal sample preparation. We expect that these tools will have immediate applications in biomedical research and the potential for longer-term applications in point-of-care diagnostic methods for detecting and monitoring disease states associated with H2S misregulation.